There is known an underpants type disposable diaper that is configured to include a barrel shaped abdomen portion formed by joining a ventral side outer sheet and a back side outer sheet at both sides; and an inner body for absorbing excrement that extends from a widthwise middle portion in an inner surface of the ventral side outer sheet to a widthwise middle portion in an inner surface of the back side outer sheet, the ventral side outer sheet and the back side outer sheet being not connected but separated at a crotch side. Such an outer sheet-split type diaper has an advantage that leg openings through which legs of a wearer are inserted do not need to be punched out or need to be punched out in smaller areas. That is, although cutout pieces for making the leg openings (hereinafter, referred to as trims) are generally disposed of, this type of a diaper can reduce material loss (hereinafter, referred to as trim loss).
FIG. 11 shows a flow of a process of manufacturing the outer sheet-spit type diapers. This manufacturing line is configured to convey diapers in a lateral direction such that a width of each diaper is oriented along a machine direction (MD) or a line flow direction. In this line, outer sheets 12F and 12B constituting an abdomen portion are formed, and an inner body 200 fabricated in another line is attached to the outer sheets 12F and 12B. For easy understanding, not separated members in the process of manufacture will be described using the same reference numerals as those given to the separated members in a finished product.
To describe in more detail, this manufacturing line mainly includes an elastic member attaching step 301, an elastic member cutting step 302, an outer sheet cutting/splitting step 304, an inner body attaching step 307, a folding step 308, a side portion joining step 309, and a separating step 310.
Specifically, at the elastic member attaching step 301, a band-like sheet base material 12 of a predetermined width is conveyed in a direction of continuation thereof while elongated elastic members 15 to 19 such as rubber threads are fixed in a state of being stretched in the MD direction to the almost entire band-like sheet base material 12 at intervals in a CD direction; and another band-like sheet base material 12 of a predetermined width is supplied and bonded to the top surface of the former sheet base material 12 in a direction of continuation thereof. In addition, if necessary, the elastic member cutting step 302 is performed to cut the elastic members 15, 16, 18, and 19 positioned in a section CT which will overlap the inner body 200, at predetermined intervals in the MD direction, using a cutting device such as a heat embosser or the like, so that the elastic members 15, 16, 18, and 19 do not act stretching force on the section CT.
Next, at the outer sheet cutting and splitting step 304, a predetermined middle portion SL in the CD direction of the band-like sheet base material 12 is cut by a slitter in the MD direction to split the sheet base material 12 into the portion to be the ventral side outer sheet 12F and the portion to be the back side outer sheet 12B; and a space between the outer sheets 12F and 12B is increased up to a predetermined distance. After the slitting, end edges 12L on the center side in the CD direction of the outer sheets 12F and 12B (constituting edges of leg openings LO) are cut off in a curved line.
After that, at the inner body attaching step 307, the inner body 200 fabricated in advance in another line is supplied at predetermined intervals in the MD direction, and is fixed to the portion to be the ventral side outer sheet 12F and to the portion to be the back side outer sheet 12B so as to straddle the two materials.
Then, at the folding step 308, the portion to be the ventral side outer sheet 12F and the portion to be the back side outer sheet 12B are folded in the CD direction such that surfaces thereof for attachment of the inner body 200 overlap each other. Next, at the side portion joining step 309, the portion to be the ventral side outer sheet 12F and the portion to be the back side outer sheet 12B are joined together at both ends of individual diapers. Then, at the separating step 310, the portion to be the ventral side outer sheet 12F and the portion to be the back side outer sheet 12B are cut at boundaries between individual diapers to thereby obtain individual diapers DP.